As a conventional example of a fluid machine, Japanese Unexamined Patent Publication No. H6-288358 discloses a compressor having an eccentric rotation piston mechanism achieved by a cylinder having an annular cylinder chamber and an annular piston which is contained in the cylinder chamber to make eccentric rotation. The fluid machine compresses a refrigerant by making use of volumetric change in the cylinder chamber caused by the eccentric rotation of the piston.